The present invention relates to a vane type rotary pump, and more particularly to a vane type rotary pump, for example, suitable for use in a vehicle power steering system.
In a conventional vane type rotary pump of this kind, there is provided a flow control valve in which a spool is displaced by the difference in pressure acting on its opposite ends to permit the flow of an excessive amount of discharged fluid into a bypass passage when the rotational speed of the pump has exceeded a predetermined value thereby to constantly supply a predetermined quantity of pressurized fluid into a hydraulic circuit for the power steering system. In such a control of the discharged fluid, the excessive amount of fluid flowing into the bypass passage increases in accordance with increase of the rotational speed of the pump. This results in increase of the load torque in operation of the pump.